One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(9,10)(11,15)(12,17)(13,16)(14,19)(18,26)(20,28)(21,27)(22,30)(23,33)(24,31)(25,29)(32,36)(34,40)(35,38)(37,39) involution — undirected(2,5)(3,8)(6,7)(9,11,14,22)(10,15,19,30)(12,20,23,34)(13,25,26,21)(16,27,18,29)(17,28,33,40)(24,37,36,35)(31,38,32,39)(10,16,19,18)(12,23)(15,27,30,29)(17,32,33,31)(20,34)(24,36)(28,39,40,38)(35,37)(2,6)(5,7)(9,12,14,23)(10,17,19,33)(11,20,22,34)(13,24,26,36)(15,28,30,40)(16,31,18,32)(21,35,25,37)(27,38,29,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.